The present invention relates to an irradiation apparatus such as a microtron or linear accelerator (lineac) for treating a treated body by irradiating the foci of a treated body with beams of charged particles or radiation beams of high energy.
In the radiation therapy, it is important to irradiate only the focus with charged particles beams or radiation beams while the radiation exposure of a normal tissue around the focus is suppressed as much as possible. In that sense, it is significant to use an irradiation synchronized with respiratory cycle. The irradiation synchronized with respiratory cycle is one such that the above-mentioned charged particles beams or radiation beams are irradiated on the focus in synchronism with a rest period of a focus which is being moved by a respiratory movement. According to the irradiation synchronized with respiratory cycle, there can be carried out a more ideal radiation therapy as compared with a general irradiation method in which a focus is irradiated while an irradiation field is widened so as to cover all ranges in which the foci are being moved.
Heretofore, such an irradiation synchronized with respiratory cycle has been described in "Study of Irradiation Synchronized with Respiratory Cycle" (written by Kiyoshi Ohhara, et al.: Japanese Journal of Irradiation in Medicine, Vol. 47, No. 3, pp. 44 to 52, 1987). According to this irradiation synchronized with respiratory cycle, intermittent irradiation is performed in synchronism with respiration by turning on and off a microwave oscillator such as a magnetron or a klystron for exciting the acceleration potential.
However, according to the above-mentioned conventional technology, when this technology is applied to the microtron and the lineac, a delay of irradiation occurs in a respiration synchronizing signal due to a time delay without a reproducibility produced until an oscillator reaches an original microwave output immediately after the oscillator is energized. As a result, it is not possible to perform intermittent irradiation in synchronism with respiration. Also, when this technology is applied to the lineac, energy the charged particle beam is determined depending on, in particular, a microwave output and an electron gun output so that energy of the electron beam becomes unstable. Besides, since such delay of irradiation (unstable intermittent irradiation in synchronism with respiration) occurs, the energy becomes unstable at every respiration. There is then presented the problem that they are accumulated with a lapse of time and become much more remarkable.